Remote detonation system

ABSTRACT

In a remote detonation system wherein a plurality of underwater explosives are detonated simultaneously by command signals sent from a remote control station, there are provided a control station including an oscillator for generating a plurality of frequency modulated waves and a sound wave transmitter for transmitting the frequency modulated waves through the water as frequency modulated command signals; a plurality of detonation control elements, each including a sound wave receiver for receiving the frequency modulated command signals from the control station, means for demodulating the output from the sound wave receiver for reproducing the frequency modulated command signals and ignition means including a plurality of switches which are operated sequentially by the output of the demodulating means; a plurality of electric detonators each connected to the ignition means of the detonation control elements, and a plurality of underwater explosives detonated by the detonations of respective electric detonators.

Waited States Patent [1 1 Shimizu et al.

[451 Dec. 25, 1973 REMOTE DIETONATION SYSTEM [73] Assignees: 0K1Electric Industry (10., Ltd.;

Taisei Corporation, Tokyo, Japan [22] Filed: Oct. 16, 1972 [21] Appl.No.: 297,985

[30] Foreign Application Priority Data 1.062.320 7/1959 Germany 102/23Primary ExaminerVerlin R. Pendegrass Attorney-C. Yardley Chittick et a1.

[ 5 7 ABSTRACT In a remote detonation system wherein a plurality ofunderwater explosives are detonated simultaneously by command signalssent from a remote control station, there are provided a control stationincluding an oscillator for generating a plurality of frequencymodulated waves and a sound wave transmitter for transmitting thefrequency modulated waves through the water as frequency modulatedcommand signals; a plurality of detonation control elements, eachincluding a sound wave receiver for receiving the frequency modulatedcommand signals from the control station, means for demodulating theoutput from the sound wave receiver for reproducing the frequencymodulated command signals and ignition means including a plurality ofswitches which are operated sequentially by the output of thedemodulating means; a plurality of electric detonators each connected tothe ignition means of the detonation control elements, and a pluralityof underwater explosives detonated by the detonations of respectiveelectric detonators.

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REMOTE DETONATION SYSTEM BACKGROUND OF THE INVENTION This inventionrelates to a remote detonation system, more particularly a novel systemfor simultaneously detonating a pluraltiy of explosives loaded in aunderwater rock by using a frequency modulated signal transmitted from aremote control station.

Heretobefore, in order to explode an underwater rock with explosives bya signal transmitted from a remote control station it has been thepractice to drill a plurality openings through the rock, chargeexplosives provided with electric detonators in respective openings,electrically connect the detonators in series or parallel, and connectthe detonators to a control switch located in the remote control stationthrough an electric cable whereby the plurality of explosives aredetonated simultaneously. Such a system, however, requires to use asubmergible cable and to connect it with respective electric detonatorsin water. For this reason, there are such disadvantages that the cableis broken by a tidal current, that the electrical connections betweenthe cable and the electric detonators are damaged and that the cablebecomes tangled. Thus, the working effi' ciency is low so that it hasbeen impossible to use such a system in deep water.

To eliminate the use of an electric cable it has been proposed to useultrasonic waves. However, ultrasonic receivers associated with thedetonators often respond to underwater noises thus there is probabilityof causing unexpected detonations resulting in disasters. Furthermore,where it is necessary to detonate a large underwater ground area byusing a large number of explosives it has been difficult tosimultaneously detonate them due to the difference in times of thearrival of the supersonic waves to respective detonators, therebydecreasing the efficiency of detonation.

SUMMARY OF THE INVENTION Accordingly, it is an object of this inventionto provide a new and improved remote induction detonation system usingultrasonic wave and capable of safely and accurately detonate adetonator without the fear of any miss-detonation caused bymiss-connection or breakage of a cable and which is not required to useany underwater cable or electrical conductor which should be connectedto the detonator under water.

Another object of this invention is to provide a novel remote inductiondetonation system using ultrasonic wave which can safely andsimultaneously detonate a plurality of detonators from a remote pointwithout being interferred by underwater noises even in applicationswhere the conventional system using an electrical cable is not practicaldue to a rapid tidal current or a large depth.

A further object of this ivnention is to provide a novel remoteinduction detonation system utilizing ultrasonic wave wherein a maindetonator is firstly detonated by a command signal transmitted from aremote control station and then a plurality of auxiliary detonators aredetonated simultaneously by the cooperation of said command signal andthe percussion wave generated by the explosion of the main detonator.

Still further object of this invention is to provide a novel detonationcontrol circuit or element which accurately responds only to thedetonation command signal for electrically detonating the detonator.

According to this invention there is provided a remote detonation systemwherein a plurality of underwater explosives are detonatedsimultaneously by command signals sent from a remote control station,characterized in that there are provided a control station including anoscillator for generating a plurality of frequency modulated waves and asound wave transmitter for transmitting the frequency modulated wavesthrough the water as frequency modulated command signals; a plurality ofdetonation control elements, each including a sound wave receiver forreceiving the frequency modulated command signals from the controlstation, means for demodulating the output from the sound wave receiverfor reproducing the frequency modulated command signals and ignitionmeans including a plurality of switches which are operated sequentiallyby the output of the demodulating means; a plurality of electricdetonators each connected to the ignition means of the detonationcontrol element; and a plurality of underwater explosives detonated bythe detonations of respective electric detonators.

BRIEF DESCRIPTION OF THE DRAWINGS Further objects and advantages willbecome apparent from the following detailed description taken inconjunction with the accompanying drawings in which:

FIGS. 1 and 2 are diagrams to show basic arrangements of slightlydifferent remote detonation systems embodying the invention wherein inthe arrangment shown in FIG. 1 both the main detonator and a pluraltiyof auxiliary detonators are installed at a substantially equalunderwater level whereas in the arrangement shown in FIG. 2 the maindetonator is located at a higher underwater level.

FIG. 3 shows a block diagram of one example of a control station used inthis invention;

FIG. 4 shows a block diagram of a detonation control circuit associatedwith the main detonator;

FIG. 5 shows a block diagram ofa detonation control circuit for theauxiliary detonators;

FIG. 6 shows connection diagram ofa ignition circuit for igniting adetonator;

FIG. 7 shows a block diagram of one example of the timing circuit usedin the control station used in this invention;

FIG. 8 shows a block diagram of one example of a timing circuit utilizedin a detonator of this invention and FIG. 9 shows waveforms of variouscircuit elements utilized in the timing circuit shown in FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The remote detonation systemshown in FIG. 1 comprises a control station 1 for transmitting apluraltiy of frequency modulated command signals through a ultrasonicsound transmitter 2 immersed in water, a main detonation control element4 located at the bottom of the water and provided with a sound wavereceiver 3 for receiving the frequency modulated command signalstransmitted from transmitter 2. An electric detonator 5 is included inthe detonation control element 4 for detonating an explosive 6. Thereare also provided a plurality of sound wave receivers 8,, 8 8,. arrangedto receive the frequency modulated command signals transmitted from thetransmitter 2 and the percussion wave generated by the detonation of themain explosive 6 for actuating detonation control elements 9,, 9 9,,respectively which are connected to electric detonators 9,, 9 9,,associated with auxiliary explosives 11,, 11 11,, loaded in the holes onthe rock at the bottom of the water.

A plurality of frequency modulated command signals radiated byultrasonic wave transmitter 2 of the control station 1 propergatethrough the water to be received by the wave receiver 3 of the maindetonation control element 4 and a plurality of wave receivers 8,, 8 8,,of the auxiliary detonation control elements 9,, 9 9,,. The maindetonation control element 4 located at the bottom of the water operatesto sequentially demodulate and detect a series of the frequencymodulated command signals which are received by wave receiver 3 fordetonating electric detonator 5 and explosive 6 by the output of themain detonation control element 4. On the other hand, wave receivers 8,,8 8,, of the auxiliary detonation control elements 9,, 9 9, operate toreceive predetermined signals among a series of the frequency modulatedcommand signals and an intense percussion wave generated by theexplosive of the main explosive 6, thereby energizing respectiveelectric detonators 10,, 10 10,, by their outputs in response to thepredetermined signals and the percussion wave for simultaneouslydetonating auxiliary explosives 11, 12, 11,,.

In the modified embodiment shown in FIG. 2, the detonation controlelement 4 is floated on the surface of the water, and wave receiver 3,'and a detonator 5 associated with the main explosive 6 are suspendedfrom and electrically connected to the detonation control element 4. Thelevels of the wave receiver 3, the detonator 5 and the main explosive 6may be relatively shallow.

As above described, the control station 1 utilized in this invention isdesigned to generate a plurality of frequency modulated command signalsbut for the sake of brevity it is herein assumed that the controlstation generates two such signals. In the embodiment shown in FIG. 3,there is provided a carrier wave oscillator 12 for supplying a carrierwave of frequency f, (for example KHz) to a frequency modulator 16.There are also provided modulation signal oscillators l3 and 14 forgenerating modulation signals of frequenciesf, (for example 500 Hz) andf(for example 400 Hz). The modulation signal f, from the modulationsignal oscillator 13 is supplied to the frequency modulator 16 for apredetermined interval through a timing gate circuit 15, whereas themodulation signal f from the modulation signal oscillator 13 is suppliedto the frequency modulator 16 for another predetermined interval alsothrough the timing gate circuit 15. As a result, the output from thefrequency modulator 16 comprises, a command signal produced by frequencymodulating the carrier wave f,, with signal f, followed by a commandsignal produced by frequency modulating the carrier wave f with signal fThese two frequency modulated command signals are amplified by a poweramplifier 17 and then radiated into the water through the ultrasonicwave transmitter 2. The ultrasonic waves are received by the main andauxiliary wave receivers 3 and 8,, 8 8

Referring now to FIG. 4, the two frequency modulated command signalsreceived by the receiver 3 ofthe main explosive 6 are amplified by anamplifier l8 and their amplitudes are limited to a constant level by alimiter 19. The outputs of the limiter are demodulated by a demodulator20 and are then separated into two command signals f, and f, by bandpassfilters f, and f, having narrow passbands. After being amplified by anampifier 23, the signalf, is rectified by a rectifying and integratingcircuit 24 to cloe a first switch 25 of the ignition circuit 25.Although the detail of this switch will be described later, it isconstructed such that it is maintained in the closed condition for apredetermined interval once it has been closed. On the other hand, thecommand signal f from the bandpass filter 22 appears later than theoutput signal f, from the bandpass filter f, and the signal f, is usedto close a second switch 28 through an amplifier 26 and a rectifying andintegrating circuit 27. When first and second switches 25 and 26 areclosed in this manner, an ignition circuit that can be traced from asource of supply 29 to the ground via first and second switches 25 and28 and the electric detonator 5 is closed to detonate the detonator 5and hence the main explosive 6.

As shown in FIG. 5, in a detonation control element, the frequencymodulated command signals received by a wave receiver 8 are amplified byan amplifier 30 and the amplitudes of the signals are limited to adefinite level by the operation of a limiter 31. The outputs fromlimiter 31 are demodulated by a demodulator 32 and are then supplied toa bandpass filter 33. As above described, since the auxiliary detonationcontrol element is designed to detect only a predetermined signal amonga number of frequency modulated command signals received by the receiver8, the bandpass filter 33 is designed to pass only the command signalhaving frequency f,. Accordingly, the filter 33 produces an output onlywhen the command signal is modulated by frequency f,. The output fromthe demodulator 33 closes a first switch 36 via an amplifier 34 and arectifier 35. Under these conditions, as has been described hereinabove, since the main explosive 6 has already been detonated, an intensepercussion wave generated thereby is received by the wave receiver 8 anda signal from this receiver is transformed into a high voltage pulsewave having a steep wavefront by means ofa limiter 38 and this pulsewave exceeds the predetermined level to close a second switch 39 in theignition circuit. As a result, current flows through an electricdetonator 10 from a source 37 via first and second switches 36 and 39thus detonating simultaneously the auxiliary explosives. Since thelimitor 38 may comprise a well known combination of a resistor, aconstant voltage diode and a diode, its detail will not be described.

FIG. 6 illustrates one example of an ignition circuit utlized in themain and auxiliary detonation control elements shown in FIGS. 4 and S.The ignition circuit shown in FIG. 5 comprises a source 41 whichcorresponds to the source 29 or 37 shown in FIG. 4 or FIG. 5. A seriescircuit including a first silicon controlled rectifier element 42 and aload resistor 43 is connected across the source 41. The gate electrodeof the silicon controlled rectifier element 42 is connected to thenegative pole of source 41 via a stabilizing resistor 44 and to aterminal 46 which receives the demodulated command signal f, through adiode 45 connected to pass current only in the forward direction,whereas the oathode electrode of the rectifier element 42 is connectedto the negative pole of the source 41 through a charging resistor 48 anda capacitor 44 which are connected in series. There is also provided asecond silicon controlled rectifier element 49 with its anode electrodeconnected to the juncture between resistor 47 and capacitor 48. Thecathode electrode of the silicon controlled rectifier element 49 isconnected to the negative pole of the source it through a load resistor58 to the same negative pole through an electric detonator 511(corresponding to the detonator 5 or 18 shown in FIG. 4 or FIG. 5). Thegate electrode of the rectifier element 49 is connected to an inputterminal 53 through a diode 52, the input terminal 53 being connected toreceive the second command signal (that is the command signalf in themain detonation control element shown in FIG. 4 or the output fromlimiter 38 in the auxiliary detonation control element shown in FIG. 5).A resistor 54 is connected between the gate electrode of the secondsilicon controlled rectifier element 49 and the negative pole of source411 for the purpose of stabilizing the operation of the gate electrode.

In operation, the positive voltage of the first command signal impressedacross the input terminals 44 and 416' is applied to the gate electrodeof the first silicon controlled rectifier element 42 through diode 45thus turning ON the rectifier element 42. When turned ON the siliconcontrolled rectifier element 42 charges a capacitor 48 ofa relativelylarge capacity through the charging resistor 47. When the second commandsignal is impressed across input terminals 53 and 53', after thecapacitor 48 has been completely charged up, this command signal isapplied to the gate electrode of the second silicon controlled rectifierelement 49 through diode 52 thus turning ON this rectifier element 49.Conduction of the rectifier element 49 discharges capacitor 48 throughelectric detonator 51 thus detonating the same. It is to be understoodthat the resistance value of the load resistor 58 of the siliconcontrolled rectifier element 49 is made sufficiently larger than that ofthe electric detonator 51 thus ensuring a large current to flow throughthe detonator 5]..

As above described, the circuit shown in FIG. 6 operates to turn ON thefirst silicon controlled rectifier element 42 for charging the capacitor48 when it receives the first command signal and to detonate theelectric detonator when it receives the second command signal aftercompletion of the charging of the capacitor. Accordingly, the electricdetonator is detonated only when the first and second command signalsarrive consecutively or serially. In other words, the detonator will notbe operated when the two command signals are received at the same timeor in the opposite order. When connecting the ignition circuit with theelectric detonator in the field, that is when connecting the detonatoracross terminals 55 and 56, even when the silicon controlled rectifierelements 42 and 49 are inadvertently turned ON, it is possible to limitthe current flowing through the detonator to a small value not to ignitthe same because the resistance value of the charging resistor 47 is setto a high value.

FIG. 7 is a connection diagram showing a detailed connection of thetiming gate circuit shown in FIG. 3. As shown, the timing gate circuit15 comprises a detonation command switch CS, a reset switch RS, timers Tand T relay coils RL-ll, Ric-2, RL-3 and RL-4l and relay contactsoperated thereby. When the detonation command switch CS is closed, relaycoil (IL-1 is energized which is maintained in the energized conditionby a self-holding contact rl-l. Energization of relay coil RL-lenergizes relay coil lRL-Z through a contact of timer T As a result,contact r1-2 of relay coil LR-2 is closed to apply the signal fgenerated by the modulation signal oscillator 13 to the frequencymodulator l6. Concurrently therewith relay coil RL-3 is energized byrelay contact r1-2a and is self-held by its self-holding contact rl-3.When relay coil RL-2 is energized, one of its contact, not shown,disconnects the timer T from source 24V, but the timer T, continues tooperate for a preset interval. Upon termination of this preset interval,relay coil RIJ-2 is deenergized to open its contact rl-2, thusinterrupting the supply of the signal f to modulator l6. Concurrentlytherewith, relay coil RL-4 is energized through contacts rll-3, Vii-21and the contact of timer T Accordingly, the output f from modulationsignal oscillator M will be applied to frequency modulator 16 viacontact r1-4. The supply of output f to the frequency modulator 16 isterminated when the interval set in timer T has elapsed. In this manner,by using the timing gate circuit it is possible to send out sequentiallytwo types of command signals from a single wave transmitter 2.

FIGS. 3 and 7 illustrate an embodiment of this invention wherein aplurality of command signals are transmitted sequentially from a controlstation and these serial command signal waves are received by remotedetonation control elements. However, it should be understood that thesame object can be accomplished by simultaneously transmitting aplurality of command signals from the control office, receiving thesecommand signal waves at the remote detonation control elements,transforming these simultaneously received control signal waves intotrains of serial signals, and supplying the trains to respectiveignition circuits. In such a modification, it is not necessary to usethe timing gate circuit shown in FIG. 3 and the circuit between thebandpass filters 2ll and 22 and switches 25 and 28 of the detonationcontrol element shown in FIG. 4 may be replaced by the timing circuitshown in FIG. 8. More particularly, as shown in FIG. 8, the output fromthe bandpass filter 21 is supplied to a rectifying and integratingcircuit 57 and the output thereof is coupled to a Schmit circuit 59. Theoutput from the Schmit circuit 59 is applied to serially connectedmonostable multivibrators 61 and 62. On the other hand, the output fromthe bandpass filter 22 is applied to a Schmit circuit 60 through arectifying and integrating circuit 58. The output from monostablemultivibrator 61 is supplied to a terminal 63 leading to the firstswitch 25 of the ignition circuit shown in FIG. 4, whereas the outputsfrom Schmit circuit 60 and monostable multivibrator 62 are coupled to aterminal 65 leading to the second switch 28 via an AND gate circuit 64.

In the arrangement shown in FIG. 8, since first and second controlsignals f and f arrive at the inputs and bandpass filters 21 and 22 atthe same time, the inputs to these filters re shown by waveforms A andB, respectively, of FIG. 9. These waveforms are transformed intowaveforms C and D by the action of the rectifying and integratingcircuits 57 and 58. Schmit circuits 59 and 60 are triggered respectivelyby the outputs of the rectifying and integrating circuits 57 and 58 toproduce waves as shown by FIG. 9E. The output from Schmit circuit 59triggers the monostable multivibrator 61 for supplying to the monostablemultivibrator 62 and terminal 63 a pulse, FIG. 9F, having a pulse widthdetermined by the time constant of the monostable multivibrator 611. Theoutput supplied to terminal 63 is used to operate the first switch 25.The output from the monostable multivibrator 62 is shown by FIG. 9G andis supplied to AND gate 64 together with the output, FIG. 9E, of Schmidcircuit 60 so that an output, FIG. 9H, corresponding to the logicalproduct of these two signals is applied to terminal 65 for operating thesecond switch 28. As above described, by using the timing circuit shownin FIG. 8, it is possible to convert plurality of command signals whichare received simultaneously into sequential or series command signalsfor sequentially closing the switches of discrete ignition circuits.

In the embodiment of the auxiliary detonation control element shown inFIG. 5, instead of using circuit elements 30 through 35 which are usedfor processing the signals for actuating the first switch 36 bydetecting a prescribed command signal it is also possible to use a wellknown mechanical or electrical timer which is constructed to operate fora predetermined interval for closing the first switch 36 and maintainingthe same in the closed condition, the predetermined intervalcorresponding to the interval in which the detonation command signal istransmitted from the control station.

Various types of the processing circuit may be substituted for theprocessing circuit including various circuit elements starting from thebandpass filter to the switches shown in FIGS. 4 and 5. Thus forexample, it is also possible to apply the output from the bandpassfilter to a differentiating circuit for driving the monostablemultivibrator with the differentiated signal. The output of themonostable multivibrator is then integrated for operating the switchwith the output of the integrator. Alternatively, the output from thebandpass filter may be applied to a slicer for driving a flip-flopcircuit with the sliced output from the slicer. The output of theflip-flop circuit is integrated for operating the switch with outputfrom the integrator.

Although in the embodiments shown in FIGS. 4 and the main and auxiliarydetonation control elements are used for inducing the detonation of theauxiliary explosives by the percussion wave generated by the detonationof the main explosive, it will be clear that the invention is by nomeans limited to these particular embodiments and that instead of usingauxiliary detonation control elements, it is also possible to use aplurality of main detonation control elements, each constructed as shownin FIG. 4.

Further, although in the foregoing embodiments, two types of thefrequency modulated command signals were used it is also possible to usethree or more types of the frequency modulated command signals from thestandpoint of safety. In such a case, it is necessary to use switches inthe ignition circuit of the same number as that of the frequencymodulated command signals.

What is claimed is:

1. A remote detonation system comprising a control station includingoscillator means for generating a plurality of frequency modulated wavesand a sound wave transmitter for transmitting said frequency modulatedwaves through water as frequency modulated command signals; one or aplurality of detonation control elements, each including a sound wavereceiver for receiving said frequency modulated command signals fromsaid control station, means for demodulating the output from said soundwave receiver for reproducing said frequency modulated command signalsand ignition means including a plurality of switches which are operatedsequentially by the output of said demodulating means; a plurality ofelectric detonators each connected to said ignition means of saiddetonation control element; and a plurality of underwater explosivesdetonated by the detonations of respective electric detonators.

2. A remote demodulation system comprising a control station includingoscillator means for producing a plurality of frequency modulated wavesand a sound wave transmitter for transmitting said frequency modulatedwave through water as frequency modulated command signals; a maindetonation control element including a first sound wave receiver forreceiving said frequency modulated command signals from said controlstation, means for demodulating the output from said sound wave receiverfor reproducing said frequency modulated command signals, and ignitionmeans including a plurality of switches which are operated sequentiallyby the output of said demodulating means; an electric detonatorconnected to said ignition means of said main detonation controlelement; a underwater main explosive detonated by the detonation of saidelectric detonator; a second sound wave receiver for receiving saidfrequency modulated command signals from said control station and thepercussion wave generated by the detonation of said main explosive; aplurality of auxiliary detonation control elements, each including meansfor selectively demodulating the output from said second sound wavereceiver for reproducing only a predetermined one of said frequencymodulated command signals, level setting means connected to said secondsound wave receiver for detecting and transforming the receivedpercussion wave into an electric signal, and ignition means includingswitch means operated by the outputs of said demodulating means and saidlevel setting means; a plurality of auxiliary electric detonators eachconnected to said ignition means of said auxiliary detonation controlelement; and a plurality of underwater auxiliary explosives eachdetonated by the detonation of said auxiliary electric detonator.

3. The remote detonation system according to claim 1 wherein saidoscillation means of said control station comprises a carrier waveoscillator, a plurality of modulation signal generators, a frequencymodulator connected to said carrier wave oscillator, a timing gatecircuit for sequentially applying the outputs of said plurality ofmodulation signal generators; and a power amplifier to amplify theoutput from said frequency modulator for supplying the amplified outputto said sound wave transmitter.

4. The remote detonation system according to claim 2 wherein saidoscillation means of said control station comprises a carrier waveoscillator, a plurality of modulation signal generators, a frequencymodulator connected to said carrier wave oscillator, a timing gatecircuit for sequentially applying the outputs of said plurality ofmodulation signal generators; and a power amplifier to amplify theoutput from said frequency modulator for supplying the amplified outputto said sound wave transmitter.

5. The remote detonation system according to claim 2 wherein thedemodulating means of said main detonation control element comprisesmeans for detecting a plurality of simultaneously received frequencymodulated command signals and timing means for arranging in parallel theoutputs of said detecting means.

6. The remote detonation system according to claim 2 wherein saidauxiliary explosives controlled by said auxiliary detonation controlelements are located at the bottom of water.

7. The remote detonation system according to claim 1 wherein two typesof said frequency modulated command signals are used.

8. The remote detonation system according to claim 2 wherein two typesof said frequency modulated command signals are used,

9. The remote detonation system according to claim 3 wherein thedemodulating means of said main detonation control element comprises anamplifier for amplifying the output of said sound wave receiver, alimiter for limiting the amplitude of the output of said amplifier, ademodulator for demodulating the frequency modulated output of saidlimiter, a plurality of bandpass filters for filtering respectivecommand signals out of the output from said demodulator, and arectifying and integrating circuit to rectify and integrate the outputsfrom said bandpass filters for operating said switches of said ignitionmeans.

10. The remote detonation system according to claim 8 wherein saidtiming circuit comprises a first rectifying and integrating circuitresponsive to the detected output of a first command signal, a firstSchmit circuit triggered by the output from said first rectifying andintegrating circuit, a first monostable multivibrator triggered by theoutput from said first Schmit circuit, a second monostable multivibratortriggered by the output from said first monostable multivibrator, asecond rectifying and integrating circuit response to the detectedoutput of a second command signal, a second Schmit circuit triggered bythe output from said second rectifying and integrating circuit, an ANDgate circuit connected to receive at its inputs the output from saidsecond monostable multivibrator and the output from said second Schmitcircuit, means responsive to the output of said first monostablemultivibrator for actuating a first switch of said ignition means, andmeans responsive to the output from said AND gate circuit for actuatinga second switch of said ignition means.

11. The remote detonation system according to claim 8 wherein saidignition means comprises a source of supply, a series circuit includinga first silicon controlled rectifier element and a load resistor, saidseries circuit being connected across said source, a first inputterminal connected to the gate electrode of said first siliconcontrolled rectifier element for receiving a first input signal, asecond series circuit including a charging resistor and a capacitor,said second series circuit being connected across the cathode electrodeof said first silicon controlled rectifier element and the negative poleof said source, a second silicon controlled rectifier element with itsanode electrode connected to the juncture between said charging resistorand said capacitor, means to connect an electric detonator across thecathode electrode of said second silicon controlled rectifier elementand the negative pole of said source, and a second input terminalconnected to the gate electrode of said second silicon controlledrectifier element for receiving a second input signal.

1. A remote detonation system comprising a control station includingoscillator means for generating a plurality of frequency modulated wavesand a sound wave transmitter for transmitting said frequency modulatedwaves through water as frequency modulated command signals; one or aplurality of detonation control elements, each including a sound wavereceiver for receiving said frequency modulated command signals fromsaid control station, means for demodulating the output from said soundwave receiver for reproducing said frequency modulated command signalsand ignition means including a plurality of switches which are operatedsequentially by the output of said demodulating means; a plurality ofelectric detonators each connected to said ignition means of saiddetonation control element; and a plurality of underwater explosivesdetonated by the detonations of respective electric detonators.
 2. Aremote demodulation system comprising a control station includingoscillator means for producing a plurality of frequency modulated wavesand a sound wave transmitter for transmitting said frequency modulatedwave through water as frequency modulated command signals; a maindetonation control element including a first sound wave receiver forreceiving said frequency modulated command signals from said controlstation, means for demodulating the output from said sound wave receiverfor reproducing said frequency modulated command signals, and ignitionmeans including a plurality of switches which are operated sequentiallyby the output of said demodulating means; an electric detonatorconnected to said ignition means of said main detonation controlelement; a underwater main explosive detonated by the detonation of saidelectric detonator; a second sound wave receiver for receiving saidfrequency modulated command signals from said control station and thepercussion wave Generated by the detonation of said main explosive; aplurality of auxiliary detonation control elements, each including meansfor selectively demodulating the output from said second sound wavereceiver for reproducing only a predetermined one of said frequencymodulated command signals, level setting means connected to said secondsound wave receiver for detecting and transforming the receivedpercussion wave into an electric signal, and ignition means includingswitch means operated by the outputs of said demodulating means and saidlevel setting means; a plurality of auxiliary electric detonators eachconnected to said ignition means of said auxiliary detonation controlelement; and a plurality of underwater auxiliary explosives eachdetonated by the detonation of said auxiliary electric detonator.
 3. Theremote detonation system according to claim 1 wherein said oscillationmeans of said control station comprises a carrier wave oscillator, aplurality of modulation signal generators, a frequency modulatorconnected to said carrier wave oscillator, a timing gate circuit forsequentially applying the outputs of said plurality of modulation signalgenerators; and a power amplifier to amplify the output from saidfrequency modulator for supplying the amplified output to said soundwave transmitter.
 4. The remote detonation system according to claim 2wherein said oscillation means of said control station comprises acarrier wave oscillator, a plurality of modulation signal generators, afrequency modulator connected to said carrier wave oscillator, a timinggate circuit for sequentially applying the outputs of said plurality ofmodulation signal generators; and a power amplifier to amplify theoutput from said frequency modulator for supplying the amplified outputto said sound wave transmitter.
 5. The remote detonation systemaccording to claim 2 wherein the demodulating means of said maindetonation control element comprises means for detecting a plurality ofsimultaneously received frequency modulated command signals and timingmeans for arranging in parallel the outputs of said detecting means. 6.The remote detonation system according to claim 2 wherein said auxiliaryexplosives controlled by said auxiliary detonation control elements arelocated at the bottom of water.
 7. The remote detonation systemaccording to claim 1 wherein two types of said frequency modulatedcommand signals are used.
 8. The remote detonation system according toclaim 2 wherein two types of said frequency modulated command signalsare used.
 9. The remote detonation system according to claim 3 whereinthe demodulating means of said main detonation control element comprisesan amplifier for amplifying the output of said sound wave receiver, alimiter for limiting the amplitude of the output of said amplifier, ademodulator for demodulating the frequency modulated output of saidlimiter, a plurality of bandpass filters for filtering respectivecommand signals out of the output from said demodulator, and arectifying and integrating circuit to rectify and integrate the outputsfrom said bandpass filters for operating said switches of said ignitionmeans.
 10. The remote detonation system according to claim 8 whereinsaid timing circuit comprises a first rectifying and integrating circuitresponsive to the detected output of a first command signal, a firstSchmit circuit triggered by the output from said first rectifying andintegrating circuit, a first monostable multivibrator triggered by theoutput from said first Schmit circuit, a second monostable multivibratortriggered by the output from said first monostable multivibrator, asecond rectifying and integrating circuit response to the detectedoutput of a second command signal, a second Schmit circuit triggered bythe output from said second rectifying and integrating circuit, an ANDgate circuit connected to receive at its inputs the output from saidsecond monostable multivibrator and the output from said second Schmitcircuit, means responsive to the output of said first monostablemultivibrator for actuating a first switch of said ignition means, andmeans responsive to the output from said AND gate circuit for actuatinga second switch of said ignition means.
 11. The remote detonation systemaccording to claim 8 wherein said ignition means comprises a source ofsupply, a series circuit including a first silicon controlled rectifierelement and a load resistor, said series circuit being connected acrosssaid source, a first input terminal connected to the gate electrode ofsaid first silicon controlled rectifier element for receiving a firstinput signal, a second series circuit including a charging resistor anda capacitor, said second series circuit being connected across thecathode electrode of said first silicon controlled rectifier element andthe negative pole of said source, a second silicon controlled rectifierelement with its anode electrode connected to the juncture between saidcharging resistor and said capacitor, means to connect an electricdetonator across the cathode electrode of said second silicon controlledrectifier element and the negative pole of said source, and a secondinput terminal connected to the gate electrode of said second siliconcontrolled rectifier element for receiving a second input signal.